Diazo type copiers are well-known and have found extensive use in a variety of copying applications. The diazo process has, however, one undesirable side effect which has made it unpleasant to use. The developing agent utilized in the diazo process is ammonia which unfortunately emits a strong and offensive odor and provides varying degrees of discomfort for any personnel who may be exposed to it.
Various chemical and mechanical means have been implemented heretofore in an effort to lessen or eliminate these noxious ammonia fumes. Mechanical means used for this purpose include enclosed developing chambers and developing apparatus which applies the ammonia developing solution in measured amounts at the point of development. Although these mechanical devices have somewhat lessened the volume of ammonia fumes escaping into the atmosphere they have by no means solved the problem since the developing chamber of such copiers cannot be completely enclosed because the print to be developed must pass through the chamber and then out of the machine through some sort of exit aperture. Ammonia fumes can of course escape into the atmosphere either through this exit aperture or on the surface of the developed print.
In a further attempt to solve the ammonia fume problem the developing chamber may be evacuated by a vacuum source and the fumes from the chamber can be passed through a chemical solution in an effort to remove the ammonia odor. Chemical solutions used in the past to accomplish this function have often been caustic and/or messy and have generally been bulky, hard to handle liquids. In most instances such chemical solutions are also expensive to purchase and use.
Applicant has solve the problem of offensive ammonia odor by a combination of mechanical and chemical means. A plenum chamber is disposed adjacent to the output aperture of the developer chamber to trap and exhaust a large percentage of the waste ammonia gases which might otherwise escape from the chamber through this aperture. Vacuum means are also provided to remove the ammonia fumes from the plenum chamber and pass them through a novel easily replaceable filter cartridge in which they are eliminated in an efficient and inexpensive manner.